the last few days, Ive had a stinging/pinching/burning sensation where the back of my armpit meets my back....but when I look in the mirror, there is no sign of injury, rubbing the area does not recreate the pain.....it just happens on its own, out of nowhere

I do have a full bottle of 500 mg valtrex that I use for the rare cold sore outbreak.

Since I have no sign of a rash, would it be wasteful to start taking the Vatrex? or does the valtrex only help once the rash appears?